In the summer of 1819 Keats and his friend James Rice left for an extended stay on the Isle of Wight J off the southern coast of England. Keats had spent time alone on the Isle in the spring of 1817, reading Shakespeare and receiving the inspiration that led to the long poem "Endymion" as well as some of his most famous insights about the nature of art. He hoped the 1819 journey would prove equally invigorating, but he was distracted by his troubled love for Fanny Brawne. Keats had met her in December, 1818, but he was having trouble fully committing to their relationship. He wrote several letters to Fanny during his stay on the Isle, and one in particular seems to give insight into "Bright Star! Would I Were Steadfast as Thou Art." In the letter, he writes, "I have two luxuries to brood over in my walks, your loveliness and the hour of my death. O that I could have possession of them both in the same minute." Keats's biographer Aileen Ward writes that while composing the letter, Keats witnessed the planet Venus rising outside his window. At that moment, Ward says, "doubt and distraction left him; it was only beauty, Fanny's and the star's, that mattered."

"Bright Star!" considers a similar moment, and the sonnet is considered one of Keats's loveliest and most paradoxical. The speaker of the poem wishes he were as eternal as a star that keeps watch like a sleepless, solitary, and religious hermit over the "moving waters" and the "soft-fallen mask / Of snow." But while he longs for this unchanging state, he does not wish to exist by himself, in "lone splendor." Rather, he longs to be "Awake for ever" and "Pillowed upon my fair love's ripening breast." Unfortunately, these two desires—to experience love and to be eternal—do not go together. To love, he must be human, and therefore not an unchanging thing like the star. The speaker seems to reveal an awareness of this in the final line of the poem. He wishes to "live ever" in love, but to be in love means to be human, which means that the speaker and the love he feels for the woman will change and eventually die. The only other possibility he can imagine is to "swoon to death." This can be interpreted to mean that he wishes to die at a moment when he is experiencing the ecstasy of love. Despite the awareness that the speaker seems to express about the paradox of having love and immortality, the poem as a whole can also be seen as the speaker's plea to have both of these qualities, however impossible that may be.